1. Field of Invention
This invention relates to a plasma arc cutting apparatus comprising an over-center spring mechanism which very rapidly and precisely separates a cathode from an anode, moving the cathode from one operating position to a second operating position for contact arc starting.
2. Description of The Prior Art
It is known in the art generally to use a snap mechanism to move a member into or out of an operating position.
In Armstrong U.S. Pat. No. 3,367,463 an arcuate clutch shoe and a restraining pin are mounted at a drive plate intermediate a leaf spring and a brake shoe. The leaf spring co-acts with the pin to maintain the shoe to be engaged or disengaged.
O'Brien et al. in U.S. Pat. No. 2,561,405 shows a snap disc spring with a throw rod using a compression coil spring to increase the effective length of throw of the snap disc spring in moving the rod.
Rasmussen et al. in U.S. Pat. No. 2,410,680 shows a snap action mechanism with a quick snap action from an inactive to an active position embodying the use of a diaphragm.
In Sanders U.S. Pat. No. 4,791,268, a movable cathode is disclosed in a plasma torch, said cathode being automatically separated from an anode or nozzle contact by a build-up of a gas pressure opposing and overcoming a normal spring pressure whereby the torch is useable in a non-transferred mode as well as in a transferred mode.
The above are indicative of the present state of the art.